Sequence control of pressing velocity for pressure in press casting process using greensand mould
Sequence control of pressing velocity for pressure in press casting process using greensand mould
复制标题
湿砂型压铸过程压力速度顺序控制
DOI：
10.1179/136404608x362089
复制
发表时间：
2008
影响因子：
1.4
通讯作者：
Kunihiro Hashimoto
中科院分区：
文献类型：
--
作者：
R. Tasaki;Y. Noda;K. Terashima;Kunihiro Hashimoto
近年来，为了提高生产率和铸件质量，作者小组积极开发了湿砂型压铸工艺。这个过程主要由两部分组成：第一部分是用浇包将熔融金属倒入下模，第二部分是上模向下模下落以挤压熔融金属。这种湿砂铸造的特点是铸造产量的惊人增加（超过90%）和节能。为了提高生产率，应将快速压制工艺作为一项重要任务来实现。此外，该工艺的先进技术还将抑制因熔融金属温度下降而产生的冷隔和夹杂氧化膜等铸造缺陷。而其它缺陷则是由于压力增大而引起的，这是高速压制的技术难题.在湿型砂中，经常发生金属渗透，其中固化的熔融金属浸入砂粒中。因此，作者建议控制压制速度，以实现高生产能力和抑制压力的快速增加。本文提出了一种适用于各种铸型的压力机顺序速度控制的高速压制压力抑制方法。控制设计简单，理论上进行，并使用复杂的，精确的CFD模型建立了一个简单的数学模型的流体压力。给出了生产高质量铸件所允许的压力波动范围。考虑到无缺陷压制的压力约束上限，利用所提出的数学模型，在不进行试差调整的情况下，推导了多步切换速度模式。通过CFD仿真验证了该控制器对压力脉动的控制性能。
Abstract Recently, a press casting process using a greensand mould was actively developed by the authors' group to improve productivity and casting quality. This process consists mainly of two parts: in the first, molten metal is poured in the lower mould by a ladle, and in the second, the upper mould falls down toward the lower mould to press the molten metal. The feature based advantages of this greensand casting are an astonishing increase in casting yield (over 90%) and energy saving. A rapid pressing process should be realised as a vital task to achieve an increase in productivity. In addition, the advanced technique of this process will also suppress casting defects such as a cold shut and the inclusion of generated oxide film due to the temperature decrease in molten metal. As the technical problem on high speed pressing, the other defects are caused by increased pressure. Metal penetration, in which the solidified molten metal is soaked among the sand particles in greensand, often occurs. Hence, the authors propose controlling the pressing velocity in order to realise high production competence and to suppress the rapid increase in pressure. In this paper, a pressure suppression method in high speed pressing is proposed in which the sequential velocity control of the press can be applied to various casting moulds. The control design is conducted simply and theoretically, and a brief mathematical model of the fluid pressure is built using a complicated, exact model of CFD. Then, the permitted range of pressure fluctuation is given for the production of high quality casting. Considering the upper limit of the pressure constraint for defect free pressing, the switching velocity pattern of multisteps is derived using the proposed mathematical model without trial and error adjustment. The control performance for pressure fluctuation using the obtained velocity reference is checked by CFD simulations.